I call this "the primacy of colour," where people like "Sci-fi series", even if they're actually "Fantasy in space."

Sometimes they share certain themes, which then make them "mecha show" in another way.

Regardless, such semantic discussion isn't actually very fruitful :) And I recommended the shows I did regardless of them being mecha shows, or shows with mecha, but based on their other salient characteristics of genres (actual genres, such as "Drama, thriller, mystery, etc."), plots, and quality.